Australian scientists claim that fish oil containing Omega 3 fatty acids, plus a little exercise, helped overweight people to shed pounds - even if their diet remained unchanged.

Researcher Alison Hill said: "We were very surprised to see it was so effective, especially since these people were still eating whatever they wanted”.

The Australian team fed daily fish-oil doses to obese people and told them to take moderate exercise.

Another group was given sunflower oil and told to take the same 45-minute walk or run three times a week. Other test subjects received either fish oil or sunflower oil, but took no exercise.

The study found that those who took the doses of fish oil and exercised lost an average of 2kg (4.5lb) over a three- month period. The other groups, including the one which took sunflower oil, which does not contain Omega 3, lost no weight.